Device for translating reciprocating movement of a solenoid into oscillating motion



Nov. 12, 1963 A. GERSTENFELD ETAL 3,110,826

DEVICE FOR TRANSLATING RECIPROCATING MOVEMENT OF A SOLENOID INTO OSCILLATING MOTION Filed March 29, 1961 FIG. 2.

INVENTORS ARTHUR GERSTENFELD DAVID B. PALL ATTORNEYS.

United States Patent DEVECE FOR TRANSLATING RECIPROCATHNG MOVEMENT OF A SOLENOID INTG OSCHJLAT- ENG MUTIGN Arthur Gerstenfeld, Great Neck, and David B. Pall, Rosyln Estates, Nassau County, N .Y.; said Gerstenfeld assignor to Mytron Products Inc, Brooklyn, N.Y., a corporation of New York I Filed Mar. 29, 1961, Ser. No. 99,263 4 Claims. (Cl. 310-23) This invention relates to a solenoid and particularly to a device for translating reciprocating movement of a solenoid into oscillating motion, such device being referred to hereinafter as a rotary shaft drive solenoid.

The general object of the present invention is to provide a new and improved rotary shaft drive solenoid of simple inexpensive design and construction having improved characteristics over prior art devies.

Still another object of the present invention is the provision of a new and improved rotary shaft drive solenoid which can be constructed to yield different torque versus shaft position characteristics for different types of applications.

Still another object of the present invention is to provision of a new and improved rotary shaft drive solenoid having an output shaft which will exert a large starting torque when the solenoid is actuated.

Yet a further object of the present invention is the provision of a new and improved rotary shaft drive solenoid having a rotatable output shaft which is caused to rotate without imparting thereto any linearmovement.

In accordance with the present invention the solenoid includes a hollow cylindrical Winding with an armature disposed within the winding and centrally thereof for re ciprocal movement therewithin. A rotary shaft is pro vided in the solenoid which shaft is normally biased to a predetermined position. Connecting the shaft to the reciprocably movable armature is a flexible tape or band of high tensile strength material, which band is wrapped around the shaft with one end of the band secured to the shaft and the other end secured to the plunger. When the plunger moves away from the shaft it pulls the band along with it and the band thereby rotates the shaft against its normal bias.

By shaping the surface contour of the shaft in the area of engagement with the band, the torque characteristic of the solenoid can be adjusted. For instance, if the surface contour of the shaft is shaped so that the point of engage ment of the band with the shaft when the shaft is in its normal position is fairly remote from the axis of rotation of the shaft, upon energization of the solenoid there will be a relatively long lever arm through which the force exerted on the shaft by the band operates to thereby yield a relatively large starting torque to eliminate the usual small starting torque present in rotary shaft drive solenoids.

The above and other objects, characteristics and features of the present invention will be more fully understood from the following description taken in connection with the accompanying illustrative drawing.

In the drawing:

FIG. 1 is an end view of a solenoid embodying the present invention;

FIG. 2 is a sectional view taken along the line 22 of FIG. 1 and showing the solenoid in its energized or actuated condition;

FIG. 3 is a sectional view taken along the line 33 of FIG. 2;

FIG. 4 is a sectional view similar to FIG. 2, but showing the solenoid in its deenergized or normal condition; and

ice

FIG. 5 is a sectional View taken along the line 5-5 of FIG. 4.

Referring now to the drawing in detail, a solenoid embodying the present invention is generally designated therein by the reference numeral 10. The solenoid includes an electromagnetic coil or winding 12 having input leads 14, a plunger or armature 16 slidably disposed within a low friction tube 18 which defines the core of the coil, an output shaft 20 rotatably mounted in bearings 22 and 24 which bearings are supported by a bearing holder or block 26. The shaft 20 is connected to the armature 16 by a flexible element 28 for imparting motion to the output shaft in response to motion of the plunger. The output shaft is biased to its normal position by a spring 30 and the normal position is determined by complementary stops 32 and 34. Surrounding the coil in closing relation therewith is a housing 36 which is secured to the bearing support or block 26 as by a screw 38. The opposite end of the solenoid is enclosed by a cover plate 40 which is seated in a depression in the bearing block. In order to increase the magnetic flux density passing through the plunger 16, a conical stop made of magnetic material is provided, which conical stop is designated by the reference character 42. If desired, a suitable mounting bracket 44 may be secured to the housing 36, as, for example, by welding, and the mounting bracket 44 may have provision for threadedly supporting two screws 46 which may be secured to any suitable plate or the like.

Referring to the winding 12, this winding is formed in the shape of a hollow cylinder with sleece 18 frictionally disposed within the central passage therein. The sleeve 18 is preferably made of a low friction non-magnetic material such as brass to provide a low friction seat for the armature or plunger 16. It will be seen that the face of the armature or plunger 16 confronting the conical stop 42 is shaped as a hollow or concave cone complementary to the convex conical surface 48 of the conical stop 42, whereby the confronting surface area of the conical stop and of the plunger is relatively large to increase the magnetic attraction between them when the coil 12 is energized. Naturally, both the conical stop 42 and the plunger 16 are made of magnetic material whereby to greatly increase the magnetic forces present when the coil 12 is energized.

As stated before, the element 28 for connecting the reciprocably movable plunger 16 to the rotary output shaft 20 is made of flexible material of high tensile strength. For instance, it could be a thin flexible strip of high tensile strength stainless steel. In lieu thereof, fiberglass reinforced flexible plastic could be employed. As an alternative, a high tensile strength thread or wire can be employed as the element 28. In either event, and as shown in the drawing, the strap 28 is secured to the plunger 16 by a pin 50 extending through the strap and into the plunger, although other securing means could be employed such as, for instance, a high strength adhesive or even welding. The strap extends away from its area of securement to the plunger longitudinally of the plunger and tangentially of the output shaft 20 into engagement therewith about which it is wrapped, the other end of the strap being secured to the surface of the output shaft in any suitable fashion such as, for instance, a pin 52. Thus it will be seen that as the plunger moves from its normal or deactuated position as shown in FIGS. 4 and 5, to its actuated or energized position as shown in FIGS. 2 and 3, the strap 16 will move to the left and thereby rotate the output shaft 20 in a clockwise direction as viewed in FIGS. 3 and 5.

In order to reduce friction within the solenoid the output shaft 20 is mounted in low friction bearings 22 and 24 supported by the bearing block 26. As shown herein the output shaft 20 extends outwardly of the solenoid It) at both sides thereof. Naturally, if desired, the output shaft could be arranged to extend out of one side only, the other end of the shaft being disposed within a bearing which would then act as a thrust bearing as well as a rotary bearing.

To prevent longitudinal movement of the output shaft 20 the shaft is provided with grooves 54 adjacent the exterior surfaces of the bearings 22 and 24 which grooves are adapted to receive snap rings 56 which serve to eliminate longitudinal movement of the shaft.

It will be noted that longitudinal movement of the output shaft 26 is eliminated with the construction disclosed herein due to the fact that the rotation of the shaft is not dependent upon longitudinal movement thereof as in prior art devices. Heretofore, in rotary solenoids, in order to effect rotation of the output shaft the output shaft was connected to the plunger in such a fashion that the plunger and the shaft would move reciprocably together. To impart the rotary movement to the output shaft in prior art devices some track, usually in the form of a helix, is employed so that as the shaft is moved linearly, the interengagement between the track and the shaft would impart rotary movement. However, the linear movement of the shaft is often undesirable as it must be compensated for in the connection between the shaft and the device being rotated thereby. The means for effectuating this compensation often took up valuable space and, further, space had to be provided for movement of the output shaft itself.

With the rotation of the output shaft in the present invention etfectuated by applying a pure rotary moment to the output shaft through the means of the flexible strap 28 there is no linear movement whatsoever. Thus no provision must be made to compensate for such movement and the size of the package can thereby be reduced.

It will further be noted that the degree of rotation of the output shaft is dependent solely on the length of the periphery of the shaft contacting the flexible element 28 and on the stroke of the plunger 16. For a given shaft the degree of rotation is dependent solely on the length of the plunger stroke. Hence for a very small increase in the length of the solenoid 10, which increase is due to the increase in stroke length of plunger 16, a substantial increase in the rotation of shaft 20 can be effected. With a solenoid of the design and construction described and illustrated herein rotation of the shaft 20 to a full 360 can be achieved and even larger rotations are possible. Smaller amounts of rotation of the order of 90 to 180 are easily attainable. The only modification other than the change in plunger stroke necessary to increase the amount of rotation is the angular distance that the flexible element zfi is wrapped around the shaft 20, for it will be apparent that the minimum amount of wrap necessary must be equal to the angular distance of rotation of the shaft 20. However, as presently preferred, the flexible element 28 is wrapped around the shaft over an angular distance in excess of 360 to relieve the stress on the connecting means, pin 52, and on the flexible element 28 in the vicinity of such connecting means.

Still another characteristic of a solenoid embodying the present invention and particularly embodying the feature of the flexible element 28 imparting rotary motion to the shaft 20, so that the solenoid can be designed readily to rotate 'on its positive stroke either clockwise or counterclockwise. The choice of direction of rotation is dependent solely on which way the flexible element is wrapped around the shaft 20. As viewed in FIG. 5, if the flexible element is wrapped around the shaft 20 in a counterclockwise direction then the shaft will rotate clockwise on the positive stroke. Conversely, if the flexible element is mapped around the shaft 20in a clockwise direction then the shaft 20 will rotate in a counterclockwise a} I ment of the stops 32 and 34 so that they will not interfere with such rotation.

Another advantage which stems from the fact that shaft 20 moves only in a rotary fashion, there being no axial movement, is that the plunger may be permitted to move much greater distances than the prior art devices whereby to increase the efficiency of the solenoid. A study of the characteristics of plunger magnets will demonstrate that the maximum work can be achieved only with a substantial stroke. With prior art devices which yielded rotation of the output shaft only as a result of axial movement thereof, the length of the stroke had to be kept at a maximum in order to reduce the amount of axial displacement of the output shaft. Thus the work done by such a solenoid was intentionally kept quite small for a given magnet. However, with the present construction, the magnet plunger 16 can be permitted to move a substantial distance since such movement does not cause a concomitant axial displacement of the output shaft but, instead, is converted into pure rotary movement of such shaft. Hence, for a given magnet a far more efficient solenoid can be constructed. This increase in efficiency can manifest itself either in a smaller magnet (which would result in a smaller solenoid of lighter weight) or in a reduction in power input for a given magnet, or a solenoid having the same size magnet with the same input but a far increased output. Naturally, a combination of these advantages can be achieved by proper design.

As stated hereinbefore, the output shaft 20 is biased to a normal position by a spring 34). The spring 30 is secured to the shaft by being wrapped around stop 32 which is pressed fit into shaft 20, the spring then being wound several itmes around the output shaft and having its other end anchored to the bearing block 26 by being wrapped around stop 34 pressed fit into such bearing block. The spring serves to bias the shaft 20 to a position in which the stops 32 and 34 engage to thereby prevent further rotation. In this position, the connecting strap 28 has pulled the armature 16 away from the conical stop 48 to leave an air gap 58 therebetween. This condition is shown in FIGS. 4 and 5. When energy is supplied to winding 12 through input leads 14, a magnetic field will be established which sets up an attractive force between the stationary conical stop 42 and the slidably movable armature 16. This force is sufficient to overcome the force exerted by the spring 30 through the strap 28 on the armature 16 to thereby cause the armature to move to the left until it engages the conical stop. This movement of the armature to the left will pull the connecting strap 23 to the left and thereby serve to rotate the output shaft 20 in the clockwise direciton. The energized condition of solenoid It is shown in FIGS. 2 and 3. The rotation of the output shaft 2t) can be employed to operate any of a large number of devices. Upon the energy supply being discontinued to the winding 12, the magnetic field collapses to thereby substantially eliminate themagnetic attractive force between the conical stop 42 and the armature 16. Accordingly, the force exerted by the spring 3% on the output shaft 20 is sufiicient to rotate the output shaft in a counterclockwise direction until the stop 32 engages the stop 34 at which point further rotary movement of the shaft will be prevented. This counterclockwise rotation of the output shaft 20 will pull the connecting strap 28 to the right as viewed in the drawings and thereby pull the armature 16 to the right to restore it to itsdngrmal or deenergized position as shown in FIGS. 4 an One of the critical characteristics in considering rotating solenoids is the torque characteristic of the output shaft. It is fundamental that torque is equal to a twisting force times the lever arm through Which the force operates. It

I is also basic and well known that the magnetic attraction direction on the positive stroke. Naturally, in effectuating between two parts is dependent upon the spacing between V such parts and the greater the spacing the less the magnetic attraction. Thus it will be seen that most rotary shaft drive solenoids which depend upon the magnetic attraction between two relatively movable parts would have low starting torque due to the fact that the initial attraction between a movable plunger and magnetic slug would be relatively small as compared with the force at the end of the stroke. Because of the n armor of connecting plunger 1% with rotary shaft 2t? in applicants rotary shaft drive solenoid, which manner, as hereinbeforedescribed, is the flexible band 28, this variation in force exerted by the plunger on the shaft can be compensated for. The compensation takes the form of shaping the contour of the shaft ill in the vicinity where the strap 28 is wrapped around a portion of the surface of the shaft 2d. As shown herein the surface of the shaft underlying the strap 28 is shaped much like a cam. The shape is such that when the shaft is in its normal or deenergized position with the stops 32 and 34, in stopping engagement, the strap or band 28 engages a high contour portion 6% of the shaft Zltl so that when s rap exerts a force on the shaft Ell due to the a raction of the plunger 16 due to the conical stop 42 by the actuation of the coil 12, the force is exerted through a relatively large lever arm. This will increase the amount of starting torque to thereby overcome the initial or static friction resisting rotation of the shaft 2%. However, once the shaft 2% starts to rotate and the plunger 16 moves closer to the conical stop 42, the frictional forces decrease and the force exerted by the plunger increases. At this point,

i the lever arm through which the strap 23% operates to exert a turning force on the shaft Ell can be decreased and this decrease can be effected by reducing the diameter of the shaft in the area of contact during this portion of the stroke of the plunger. This is done by tapering off the high portion oil at an appropriate point of the shaft relative to the strap 28. At the completion of too stroke the strap will be engaging the low part 6?: of the shaft surface contour to thereby reduce the lever arm and hence maintain the torque at substantially constant value.

It will therefore be seen that by a proper selection of the surface contour of the shaft 2 9 a substantially uniform torque can be applied to the output shaft by the flexible strap 23 working through a variable lever arm. Likewise, any other torque characteristic can be built in to my novel rotary shaft drive solenoid by a proper contouring of the shaft Ed in the area of engagement with the strap 8.

The solenoid lb illustrated in the drawing is adapted to operate in response to encrgization by a DC. source. However, the principles involved in the construction of the solenoid are equally applicable to AC. solenoids and the design changes necessary to make solenoid Ell operate in response to alternating current energy are well within the scope of persons skilled in the art.

While we have herein shown described the preferred embodiment of the present invention and have suggested various modifications therein, it will be understood that other changes and modificat ons may be made therein within the scope of the appended claims without departing from the spirit and scope of this invention.

What we claim is:

l. A rotary shaft drive solenoid comprising, an output shaft adapted to be rotated a predetermined angular distance from a normal position to an operated position, a reciprocably movable plunger, and means for connecting said plunger to said output shaft for rotating said shaft in response to linear movement of said plunger, said connecting means including a flexible band extending away from said shaft transversely thereof, said band having an end portion wrapped around said shaft at least said predetermined angular distance when said shaft is in said normal position and having the end of said end portion fixed to said shaft, at least part of the portion of said a shaft underlying said flexible band being of non-circular cross section.

2. A rotary shaft drive solenoid comprising, a hollow electrical coil adapted to be energized and deenergized, a plunger of magnetic material slidably disposed within said cell, a rotatable output shaft extending transversely of the line of movement of said plunger for rotation a predetermined angular distance from and to a first or normal position and to and from an actuated position, and a flexible band connected at one end to said plunger and at the other end to said shaft, said band being wrapped around said shaft at least said predetermined angular distance when said shaft is in said normal position, the portion of said shaft underlying said flexible band being of non-circular cross section.

3. in a rotary shaft drive solenoid comprising, a hollow electrical coil adapted to be energized and deenergized, a stop of magnetic material fixed relati e to said coil and disposed at least in part within said hollow coil, a plunger of magnetic material slidably disposed within said coil for movement from and to a normal or decnergized position in which said plunger is spaced from said stop and to and from an actuated or energized position in which said plunger is in engagement with said step, a rotatable output shaft extending transversely of the line of movement of said plunger for rotation at predetermined angular distance from and to a first or normal position and to and from a second or actuated position concomitantly with movement of said plunger from and to its normal position and to and from its actuated position, respectively, and a flexible band connected at one end to said plunger and at the other end to said shaft, said band being wrapped around said shaft at least said predetermined angular distance when said shaft is in said normal position, Whereby to impart said concomitant rotation to said shaft from said first to said second position in response to movement of said plunger from its normal to its actuated position, a pair of stops, one fixed to said shaft and the other fixed relative to said coil, stops being engageable when said shaft is in saio normal position for preventing rotation of said shaft away from its actuated position beyond said normal position, and a spring wound around said shaft and having one end anchored to said stop fixed to said shaft and its other end anchored to the other of said stops, said spring biasing said shaft toward said normal position whereby to bias said plunger toward its normal position.

4. In a rotary shaft drive solenoid comprising, a solenoid coil, a solenoid plunger movable axially of said coi and a rotary shaft positioned with its axis of rotation transversely of the path of movement of said plunger, said plunger being movable longitudinally toward and away from s id shaft; 21 length of exible material connected to said plunger and operatively connected to said shaft transversely thereof for turning the shaft when said length of material is tensioned and moved longitudinally with said paring-er in a direction away from said shaft, said shaft and length of flexible material having parts which are in releasable engagement with each other at the start of t e movement of the plunger away from the shaft for temporarily increasing the shaft-turning torque at the start of the turnip." of the shaft when the solenoid coil is energized for moving the plunger.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A ROTARY SHAFT DRIVE SOLENOID COMPRISING, AN OUTPUT SHAFT ADAPTED TO BE ROTATED A PREDETERMINED ANGULAR DISTANCE FROM A NORMAL POSITION TO AN OPERATED POSITION, A RECIPROCABLY MOVABLE PLUNGER, AND MEANS FOR CONNECTING SAID PLUNGER TO SAID OUTPUT SHAFT FOR ROTATING SAID SHAFT IN RESPONSE TO LINEAR MOVEMENT OF SAID PLUNGER, SAID CONNECTING MEANS INCLUDING A FLEXIBLE BAND EXTENDING AWAY FROM SAID SHAFT TRANSVERSELY THEREOF, SAID BAND HAVING AN END PORTION WRAPPED AROUND SAID SHAFT AT LEAST SAID PREDETERMINED ANGULAR DISTANCE WHEN SAID SHAFT IS IN SAID NORMAL POSITION AND HAVING THE END OF SAID END PORTION FIXED TO SAID SHAFT, AT LEAST PART OF THE PORTION OF SAID SHAFT UNDERLYING SAID FLEXIBLE BAND BEING OF NON-CIRCULAR CROSS SECTION. 